Adaptive genomic changes, epigenetic resilience and new molecular tools for the conservation and recovery of Iberian brown trout endemisms (CONSIBERTROMICS) Reference: PID2022-141549OB-I0
Interest
Scientific/social interest
Freshwater ecosystems were the most affected by biodiversity losses since 1970 to nowadays acoording to the Living Planet Report. European freshwater fish species are within the groups more threatened by pollution, water extraction, habitat fragmentation, introduction of exotic species, overfishing, and releases of non-native stocks. However, the impact of climate change will become into the main threat throughout this century. Predictions about the impact of climate change are dramatic for resident salmonids in Mediterranean countries such as the brown trout because of its restricted occurrence in headstreams. Brown trout is highly appreciated by anglers in Mediterranean countries and foster regional tourism industries during summer. However, some studies advised that ongoing climatic change might dramatically affect the sustainability of these fisheries.
In Spanish rivers, brown trout have one of the richest and most diverse genetic constitutions in Europe, with up to four evolutionary distant lineages present in these populations. Currently, several Mediterranean brown trout lineages are considered separate species, many of which are listed as Vulnerable (V) or Data Deficient (DD) in the updated Red List of European Freshwater Fish. Unfortunately, the lineages of Iberian brown trout have not yet been sufficiently taxonomically revised, although they may include several endemic species, and the taxonomic binomials used in national legislation have not been updated. Despite the existence of these four distant evolutionary lineages (Adriatic, AD; Mediterranean, ME; Atlantic, AT; and Duero, DU), Spanish legislation still considers a single species, Salmo trutta, which inhabits both Atlantic and Mediterranean rivers. The species has been listed as vulnerable in the Spanish Red List since 1992.
The native populations of the AT lineage in the Iberian rivers represent a long-time divergent branch from the older AT clade distributed among Central European populations. These European populations were the source of the hatchery stocks used for restocking the Spanish rivers. Such stocking activities with non-native stocks have resulted in introgressive hybridization of native trout populations throughout the Iberian rivers. Currently, the reinforcement with non-native stocks is falling into disuse given the risk posed to native populations. Nevertheless, the presence of “black spots” of already naturalized or highly introgressed populations in many Mediterranean rivers is a serious threat to remnant native populations in neighboring areas within each basin. A previous project on Pyrenean brown trout populations developed by the same research team has indicated that warmer temperatures and lower precipitation expected from climate change will promote the introgressive hybridization between the native and the non-native fishes already present in these rivers. Therefore, the adaptive potential and hence the long-time survival of the Iberian brown trout populations may be compromised by the extended introgression of detrimental hatchery variants into the genomes of these populations.
What is the Consibertromics project proposing?
A critical point of evolutionary biology is that species are not driven to extinction before genetic factors impact them. The amount of genetic diversity within the species determines their ability to respond to environmental changes and to maintain abundant populations. Adaptation and resilience of species and populations could be the result from complementary processes such as small allele frequency changes in many loci, allele frequency changes in a few regulatory loci or heritable epigenetic modifications. Likely, all of them are necessary for the long-term persistence of the most vulnerable populations threatened by habitat degradation and the ongoing climate change. The identification of molecular markers associated with adaptive variation allows the definition of management units based on adaptive criteria.
The main goal of the present project CONSIBERTROMICS is to disentangle the evolution and adaptation of Iberian brown trout populations using different omics methodologies to assess the potential of resilience of these populations to the ongoing environmental (climate) change. Particularly to identify the most relevant genomic regions and/or biological functions involved in the diversification, adaptation, and resilience of brown trout populations within or among the native lineages and the river basins in the Iberian Peninsula. The identification of genomic regions and epigenetic changes associated with lineage divergences and environmental changes and hybridization will help to understand the adaptive processes involved in the evolutionary history of Iberian trout endemism and their resistance and resilience to ongoing climate change; will contribute to preserve and recover the native genetic pools and will provide genetic markers for monitoring the response to climate change. In addition, our conclusions may be relevant to other fish species in Mediterranean streams, because shared threats.
Who will benefit and how?
The Spanish Royal Decree 1057/2022, which approves the State Strategic Plan for Natural Heritage and Biodiversity to 2030 indicates that the natural heritage is a fundamental resource to contribute to the fight against depopulation in Spain and to move towards a more sustainable, inclusive, innovative, and resilient territory and society. Certainly, brown trout is a popular species for angling in Spain and surely its inland fisheries are contributing to the maintenance of rural isolated areas. Thus, the regional Inland Fisheries Services throughout Spain have an increase aware to maintain these fisheries.
The sixth specific objective of Consibertromics is the development of a cost-effective molecular tool based on the outlier evolutionary, hydrographical and gene expression genes. This molecular tool will assist to ongoing and future recovery plans of native wild populations, to track changes in population distributions, the spread of non-native stocks or introgressed populations, as well as in the selection of wild specimens to found native stocks, or to be involved in supportive breeding programs.
This tool also may assist to evaluate de effects of barriers’ removal on headstreams inhabited by native trout populations as such removal may spread the hybridization between native and downstream introgressed specimens or allows the arrival of native competitors to these stretches. The project has interest for all the Spanish Inland Fishery Agencies and Services of the Autonomous Communities where brown trout is present. The designed molecular tool would aid to properly tackle management activities devoted to preserve and recover native biodiversity and to maintain the recreational brown trout fisheries in Spain.
Altogether to improve management policies to guarantee a balance between conservation and exploitation, maximizing economic and social benefits while minimizing the negative effects on recruitment. Thus, our project will help to the long-time maintenance of the fishing activities to enhance national and EU tourism in the rural areas, and the retention of inhabitants in these territories.
Finally, brown trout is considered an umbrella or flagship species; thus, the results of this proposal are also relevant to conserve and restore biodiversity in all headstreams where this species is present.